There are A LOT of threads on this topic in the CC form. The consesus seems to be that there is a minimal effect +/- 25 pts if you have good credit.
Originally Posted by Lurker1999
Anecdotally some people have reported their score dipping by 30 points or so but keep in mind they fall off after 2 years regardless. So 3 years would be impossible. And after 6 months they seem to have far less of an impact on your credit score than immediately following the inquiry.